1. Field of the Invention
The present invention relates to an apparatus to fabricate the electrode plate of a lithium battery, particularly to a coating layer removing apparatus and a method for the same, which can reduce the fabrication time and promote the yield rate.
2. Description of the Related Art
Lithium batteries have advantages of high energy density, compactness, environmental protection and combination ability. Therefore, lithium batteries have been widely used in many fields. With the increasing usage, more and more manufacturers invest in the technical development of lithium batteries.
Although the lithium battery has a very large market share, the fabrication speed thereof is hard to increase. The productivity of lithium batteries is limited by the fabrication of the electric-conduction tab and the electrode plate of the conventional electrode roll. Refer to FIG. 1. The electrode plate 100 may be a positive or negative electrode plate and comprises a substrate 110 and two coating layers 120 and 130 respectively formed on two surfaces of the substrate 110. An electric-conduction tab 150 is soldered to a region of the substrate 110, which is exposed from the electrode plate 100. To increase the electricity storage within the original volume, the exposed area 140 where the electric-conduction tab 150 is joined to the electrode plate 100 should be as small as possible. In other words, the closer the exposed area 140 to the area of the electric-conduction tab 150, the higher the electricity storage of a lithium battery.
The abovementioned scheme is ideal in theory but hard to realize in practice. Because the electrode plate 100 is very thin, removing the coating layers 120 and 130 to expose the substrate 110 is usually undertaken manually, which is laborious and time-consuming. Further, a slightly greater force applied by the worker may damage the very thin substrate 110. In fact, either too great or too small a force applied by the worker would affect the quality and the discharging capability of the lithium battery.
Both the coating layers 120 and 130 must be partially removed to form the exposed areas 140. However, the conventional technology can only remove a single coating layer 120 or 130 in one cycle. In other words, at least two cycles of operation are needed to form the exposed areas 140 of a single electrode plate 110. Therefore, the manufacturers have to invest more manpower and capital to produce lithium batteries, which reduces the competitiveness of the Taiwan lithium battery manufacturers.
A Taiwan patent of application No. TW096116856 disclosed an apparatus to solve the abovementioned problem, which simultaneously heats specialized areas of the upper and lower surfaces of the electrode plate 100 and then applies a solvent to the coating layers 120 and 130 inside the heated areas. The coating layers 120 and 130 are softened and expanded by the solvent and then separated from the substrate 110. The softened coating layers 120 and 130 are mechanically removed with a scraper or a file to form the exposed areas 140 on the electrode plate 100. The prior-art patent can fast and economically fabricate the positive and negative electrode plates 100 with reliable quality.
We should admit that the Taiwan patent of application No. TW096116856 provides automatic fabrication and solves the low-productivity problem resulting from manually removing the coating layers 120 and 130 of the electrode plate 100. The prior art can obtain the exposed areas 140 with the same depth in theory. However, the variation of the thickness of the coating layers 120 and 130, the extent of heating, the extent of solvent etching and the variation of the force applied to scrape off the coating layers 120 and 130 affect the removal of the coating layer 120 and 130, in practice. Thus, the damage rate of the electrode plates 100 is still high, and the yield and quality is still unstable, in the prior art. Therefore, the competitiveness promoted by the prior art is limited.
Accordingly, the present invention proposes a coating layer removing apparatus and a method for the same to overcome the abovementioned problems.